﻿#define _CRT_SECURE_NO_WARNINGS 1

//编程初学者入门训练第123题
//BC125 小乐乐转换成绩
//https://www.nowcoder.com/practice/ba62e0d2e9824543963f72f1e926858d?tpId=107&tqId=33406&rp=1&ru=/exam/oj/ta&qru=/exam/oj/ta&sourceUrl=%2Fexam%2Foj%2Fta%3Fpage%3D3%26tpId%3D107%26type%3D107&difficulty=undefined&judgeStatus=undefined&tags=&title=

#include <stdio.h>

int main() {
    int n = 0;
    scanf("%d", &n);
    if (n >= 90 && n <= 100) {
        printf("A");
    }
    else if (n >= 80 && n <= 89) {
        printf("B");
    }
    else if (n >= 70 && n <= 79) {
        printf("C");
    }
    else if (n >= 60 && n <= 69) {
        printf("D");
    }
    else if (n >= 0 && n <= 59) {
        printf("E");
    }
    else
        printf("F");
    return 0;
}
